The present invention relates to miter boxes for use with hand saws, and specifically to a miter box which is angularly adjustable relative to a vertical pivot axis located offset on the miter box base.
Conventional miter boxes designed for use with hand saws are either nonadjustable or angularly adjustable. The nonadjustable type is most commonly made of wood or plastic and includes a trough-like body with several angled, open-topped slots cut in the walls of the trough. These slots are used for guiding the blade of a saw for making miter cuts in pieces of wood placed on the bottom of the trough. A significant disadvantage of conventional miter boxes is that the available angles of cuts to be made in the workpiece are limited by the number and position of the slots.
Another disadvantage of conventional miter boxes relates to the structure of the miter saw blade itself. In order to prevent binding of the saw, the cross-section of the blade is slightly thinner in the body of the blade than at the cutting edge. Since the slots of the miter box must be wide enough to slidingly accommodate the cutting edge, there is significant play between the body of the blade and the edges of the slot. This play often allows the saw blade to move uncontrollably in the slot and interferes with the accuracy of the cuts. In addition, the width of the slots increases through use, to the extent that the slots eventually become too wide to ensure accurate cuts, and require the disposal of the miter box.
In response to these disadvantages, the adjustable miter box was developed. Adjustable miter boxes include an elongate metallic base with a generally centrally located pivotable saw guide, and a vertically projecting miter back extending laterally from either side of the saw guide. The saw guide is pivotable about a vertical pivot axis and includes both vertical and angular adjustments. A conventional backsaw is inserted into a vertical slot in the saw guide for reciprocal horizontal sliding action. A clamping device in the saw guide engages the saw body near the cutting edge to minimize lateral play while cutting.
In one commonly available adjustable miter saw, the angular adjustment includes a generally horizontally extending semicircular flange having a plurality of notches in its peripheral edge. To lock the angular position of the semicircular flange, an elongate, vertically extending fixed edge is provided which is coplanar with the workpiece guide and is positioned to engage the notches in the semicircular flange.
Although the adjustable miter box has greater durability and allows less saw play than the nonadjustable miter box, it has significant disadvantages of its own. One such disadvantage is the lack of adequate workpiece support provided by the relatively short length of the workpiece guide.
Another disadvantage of adjustable miter boxes is that the engagement between the notched semicircular angular adjustment flange and the fixed edge allows for lateral angular play of the saw guide, resulting in inaccurate cuts. Also, the saw blade clamping device does not accommodate the significantly thicker spine of conventional backsaws used in such miter boxes. This allows for additional unwanted play of the blade in the saw guide, further decreasing cutting accuracy.
Accordingly, a first object of the present invention is to provide a hand saw-type miter box which minimizes the play of the saw blade in the saw guide.
Another object of the present invention is to provide a hand saw-type miter box which secures the angular adjustment of the saw guide, thus promoting accurate cuts.
Still another object of the present invention is to provide an adjustable miter box which includes additional support formations for supporting the workpiece during cutting, yet is also short enough to fit in a conventional miter box case or tool box.
A further object of the present invention is to provide an adjustable miter box which is designed so that the saw may be operated from either side of the miter back.